This chart shows George E. Sansoucy, P.E., LLC’s forecast of the cost to operate New York American Water Company, Inc. and two theoretical municipal water authorities through 2044. Sansoucy predicted that municipal water would be more costly in either scenario.

In 2010, people in Merrick, Bellmore, Wantagh and Seaford paid nearly five times more for tap water than people in East Meadow, Levittown, Lido Beach and Uniondale, according to an engineering firm working for the Water Authority of Southeastern Nassau County. The first four communities got their water from the company Long Island American Water. The second four got theirs from the Town of Hempstead.

Anecdotal evidence — elected officials’ statements and local residents’ frequently told stories about acquaintances who pay far less for water in neighboring hamlets — indicates that the disparity remains wide today. Yet the engineering firm, George E. Sansoucy, P.E., LLC, recently advised the WASENC against municipalizing the area’s corporate-owned water system, forecasting that the move would raise ratepayers’ water bills over the next 30 years.

More than two years have passed since the WASENC hired Sansoucy, a New Hampshire company, to carry out a study to determine whether municipalizing the area’s water system would be economically feasible. (Long Island American Water changed its name last year to New York American Water Company, Inc.) A WASENC director said in November 2013 that the study was done, but the WASENC first made it publicly available last week at www.wasenc.org.

The 70-page document is a “draft preliminary” version, according to its title. Sansoucy based the study on “publicly available information and a field inspection,” according to the document’s executive summary, which acknowledges that the firm was unable to inspect the water system’s underground infrastructure or gain an insider’s perspective on NYAW’s operations without the company’s cooperation.